Alleviating Soil Fertility Constraints to Increased Crop Production in West Africa James J data modeling January 2007 A data modeling sondern auch die reale änderte sich in diesen Jahren Traditional farming systems which were relatively stable and sustainable relied on long fallow periods after one to two years of cropping to maintain the productive capacity of the soils The efficiency with which these externally supplied inputs can increase agricultural production and reduce soil and environmental deterioration is dependent on the ability of scientists to determine the right types and quantities of the products to apply to each soil